Two-stroke internal-combustion engine



F. cHAvE 'rwo-sTRoxE INTERNAL-COMBUSTION ENGINE Aug. 15, 195o Filed Dec. 2 1, 1945 5 rl J/ om eC rw., M Mm a A a` Im m W wml@ m ABv/ l l, d Il Patented Aug. 15, 195() :Two-STROKE INTERNAL-COMBUsrIoN t I ENGINE t Fernand-Chavo, Casablanca, French Morocco Application `December 21, 1945, Serial N o. 636,305 Y. I l'n French Morocco February 2, 1945 lClaiIn. c (ICI. 1234.-24)f Y `This invention. relates to two strokes internal Vcombustion,engines and has for its primary object to provide an engine of this type of specially improved construction adapted to prevent any induction of the gaseous or explosive mixture into the crankshaft casing containing the lubrieating oil sump and therefore any contamination of said oil by said gaseous mixture and the consequent loss of its lubricating qualities.

Another object of the invention is to provide an internal combustion engine as aforesaid wherein the piston is slidably housed in a com'- pression and power chamber space defined between the cylinder head and a stationary onepiece obturator or diaphragm adapted constantly to isolate ofi vsaid space from the crankshaft cas- 111g.

A further object of the invention is to provide an internal combustion engine of the aforesaid type which while possessing the aforesaid advantages lends itself to easy structural adaptation into engines having their cylinders arranged in straightline or V or star formation.

A still further object of the invention is to provide a two strokel internal combustion engine made up of a minimum number of parts of rugged structure capable of being readilymade and assembled at cheap material and labor costs and utilisable either 'for Ipropelling vehicles or for stationary uses.

With theseand such other objects in View as willi incidentallyI appear hereafter, the invention comprises `the novel` construction and combina` tion of` parts. that will now be described in detail with reference to the accompanying diagrammatie drawing exemplifying the same and forming .a Dart of the present disclosure. In the drawing:

Y Fig. 1 is partly an elevationalV view and partly c a vertical sectional view of the improved engine showing the piston in the cylinder and the stationary cbturator or;y diaphragm closing the upper piston-receiving chamber at its lower end.

Fig. 2 is. aview similar to Fig.4 l showing the piston at theupper end of its stroke.

Fig.-3 is a separate view of the piston shownV 2 Fig. 7 is a view partly in elevation and partly in vertical section of thev bell-shaped obturator taken at right angles to Fig. 5.

Asl shown, I designates the engine cylinder the upper portion of which is provided with an opstanding internally screw-threaded stub pipe 2 adaptedto receive an ignition element such as a spark plug (not shown). The cylinder I has one of its side walls formedintegrally with a, no1- low bulge 3 forming a lay-pass duct for the gascous mixture, said cylinder wall having a pair of superimposed ports leading into said lay-pass duct. The cylinder is formed in its opposite side wall with a pair of vertically spaced ports It, 5.

The lower end of the cylinder I is provided on each side with an elongated bulge 6, l (see Fig. 2) Whose wall merges with that of the casing for the crankshaft (not shown) which is revolubly supported in bearings as usual and is linked with the piston through a connecting rod 8 having its small end hinged to a wrist pin 9.

The lower .end ofthe cylinder I is provided with a flange Ill to which is abutted the lower flange II of a one-'piece and portless bell-shaped ob` turator or diaphragm I2 the upper portion of which has grooves i3 adapted to receive piston rings (not shown) of conventional structure. The obturator flange ll has a plurality of holes I4 adapted to receive pins, bolts o1 the like for firmly securing together the cylinder and bellshaped ohturator unit and the crankshaft casing togform a rigid assembly` As illustrated in Fig. 5,.

Y the obturator I2 is provided with a pair of top chaxnfers I5 dening passages for the iiow of thengaseous mixture. A'pair of slots I5 are also provided to permit free passing of the piston portion carrying the wrist pin bosses. The ohturator I2 also has a pair of slots for the piston' axis.

The function of the one-piece and portless bellshaped obturator l2 is to isolate ofi the crankshaft casing from the chamber defined inside the piston. The particuiar dome formation of the obturator permits a very high compression rate of the inlet gases to be achieved, while its unitary character promotes cooling of its face which contacts the explosive gases.

The engine piston i8 is advantageously made of vthi-n steel in order to possess proper lightness and strength and is slidably housed between the outer wall of the obturator I2 and the inner wall of the cylinder I. The top surface of the piston I8 is provided with a deflector i9 adapted 'to deviate the gaseous mixture led into the explosion chamber and to direct it towards the upper portion of the cylinder so as to enable the same to scavenge said chamber from' burnt gases. Slightly before its top end, the piston IB is formed with grooves 20 (the number of which may vary to suit constructional requirements) adapted to receive conventional gasket rings (not shown). Slightly under the grooves 20, the piston I8 has a port 2l through which the gases may flow to the by-pass duct 3. On its opposite side and at a level lower than that of the -port ZI the piston IS has a further port 22 for the induction of gases which arrive through the inlet port 5 in the cylinder I.

The lower end of the skirt of the piston I8 has a pair of bosses 23, 24 adapted to receive the wrist pin 9 for the connecting rod 8. The bosses 23, 24 are received in the cylinder bulges (-3, 1, thereby ensuring better lubrication. A pair of slots 25 (Fig. 4) permit the piston I8 to slide along the obturator I2 without providing a complete cut (see 26 in Fig. 6).

' The operation takes place as follows:

The engine works according to the general operative principles of two stroke internal combustion engines so far as gas induction and exhaust are concerned. However, the gaseous mixture never gains access to the crankshaft casing as in prior constructions so that it cannot contaminate and spoil lubricating oil which forms a sump in said casing. As the piston I8 reaches its upper dead centre (as shown in Fig. 2) vacuum prevails in its inner chamber, whereby the gaseous mixture is drawn in through the ports and 22 which are then in coincidence. As `the piston reaches its lower dead centre, the gaseous vmixture is compressed between it and the bell-shaped obturator I2, while the port Il is Aunm'asked (as shown in Fig. 1) and the port 2I in-the piston coincides with the lower port for the by-pass duct V3 Whose upper port is simultaneously uncovered. The gaseous mixture compressed inside the piston I8 is then led to' the explosion chamber situated on the top thereof and drives out the burnt gases from the previous explosion, thereby fullling a scavenging action and is then compressed inside the explosion chamber, whereupon said gaseous mixture is ignited by the spark which owing to proper timing of the ignition means is then produced between the electrodes of the spark plug carried in the plug pipe 2.

It will be understood that owing to the improved'structure of the engine and as the rate of compression of intake gases is higher than in Van ordinary two stroke engine, their induction into the explosion chamber is more rapid. The scavenging action on burnt gases is also more complete, so that the general eciency and running conditions of the engine are improved. Furthermore the elimination of any oil entrained by the gasous mixture means a twofold economy for proper Carburation. The engine being of simple structure can be easily built from parts lending themselves to mass-production.

Another advantage of the improvedengine is that since the crankshaft casing is entirely isolated from the spaces through which the gaseous mixture travels it can be built to form a single hollow structure throughout the length of'the engine irrespective of the number of its cylinders. Y

`As above stated, the assembly comprising the cylinder, piston and isolating obturator may be duplicated or multiplied to any extent so as to provide multi-cylinder engines working on the two. stroke principle and having their cylinders arranged either in straightline formation or in 4 V formation or in star formation while preserving the 'general advantages derived from the structural principles of the engine and the provision of the gas-tightY obturator in each cylinder. Where the cylinders are arranged in star formation, `a pump should be provided to create suction in the bottom portion of those obturators belonging to downwardly extending cylinders, as will be understood from those skilled in the art.

Cooling of the engine may take place either by water or by air, for example owing to the provision of ns or gills on the outer surface of each cylinder.

- Minor constructural details may be varied without departing from .the scope of the subjoined claim.

What is claimed is:

In a two-stroke internal combustion engine having a crankshaft, a frame defining'a casing for said crankshaft, a cylinder mounted on said frame, the lower end'of said cylinder and the said casing having a pair of diametrically opposed outward elongated bulges thereon, a vhollow piston extending to form a skirt and reciprocable within said cylinder, a rod and wrist pin connecting said piston and crankshaft, a pair of anges on said skirt extending downwardly therefrom,

a pair of diame'trically opposed hollow bosses on said anges for receiving said wrist pin, said bosses reciprocable in and guided by the elongated bulges on said cylinder and casing, an inlet port located in said cylinder, an exhaust port located in `said cylinder above saidfinlet port, a hollow ybulge rigid with said cylinder forming a bypass, one port of which is inthe cylinder wall diametrically ,opposite the exhaustpcrt and the other port of which is inthe cylinder wall diametrically opposite theinlet port, a rst port in said piston skirt near its lowerend, which port when said piston is at vthe top of lits stroke coincides with the inlet port in the cylinder wall, a second port in the pistonskirt near its upper end which port when said piston is at the bottom oi its stroke coincideswith .the v lower port ofv the )oy-passl ductin thecylinder wall, the upper port of the bly-pass duct and the exhaust port in the cylinder wall both open to the areaabove vthe piston when the piston is inthe lower said position, and a one-piece portless bell-shaped obturatcrrigidly held by said casing and tightly separating said casing from the space in which said piston reciprocates, said obturator having a chamfered top Jtace and -recessesv in its side walls opening downwardlyfto permit reciprocaticn of said wrist pin.

FERNANDVCHAVE.

REFERENCES v 011131) yThe following references'arel of record in the file of this patent'.

UNITED STATES 'PATENTS 

